UC520 with POTS. Is the conversation full duplex?

We have a UC520 connected to a group of 7945 phones in the office, and Verizon POTS on the outside. If you're having a conversation with someone who happens to be an outside caller, is the conversation full duplex - meaning can both sides talk at the same time, and both sides hear the opposing side? Or is the conversation simplex switched so that only one person can talk at a time?

What might cause drop outs when the in house person speaks, and his voice cuts off the outside person's coming in?

We had a problem with nasty echo and static, so we "lowered" output attenuation and input gain on the voice ports connected to Verizon. This fixed the echo (at least so far), but it also seems to have caused a situation where the inhouse person's voice can cut off the outside person's coming in voice.

You can set the default settings on every setting of the port you can see in the running config e.g. "input gain -3" - the issue "default input gain" under voice-port config and will be set with its default value. I can paste tomorrow default configuration.

While you make changes in the voice-port settings after you finish with the changes every time issue shut - no shut on the port.

Paolo did make me think over my mistaken post and actually this gives me idea to make another test. Please enter "no vad" under voice-port of one of the fxo ports e.g. voice-port 0/1/0. Please tell me if this fix the issue. You can try this on default port configuration also.